The invention concerns a support tube for winding yarn on a bobbin.
As is known, the manufacture of synthetic and artificial textile fibres can take place with different procedures but which all have in common the extrusion step, with which, through a spinneret equipped with capillary holes, the melted product, by coagulation or by cooling, is transformed into bands of elementary thread which constitute the so-called “filament” or yarn.
The yarn thus produced therefore needs to be wound onto a suitable support for forming the bobbin. Consisting of a tubular body, defined with the generic term “tube” and realized in cardboard or in another material suitable for the purpose, which is equipped on its side surface with an indentation for attaching or intercepting the end of the yarn to be wound on the support itself and where both the interception of the yarn and it subsequent winding on the tubular body take place with per se known automatic devices substantially resembling winding reels rotating on their own longitudinal axis, on which the tube to be wound is threaded.
Such a yarn-capturing indentation can take on different configurations, according to the characteristics of the yarn to be wound, all of which however can be sorted into three types:                yarn-gathering cut: consists of a circumferential cut, in which, the section of the groove has at least one first angular portion with a wider profile, which is used to capture the end of the yarn, and at least one remaining portion with a thinner profile, which is used to block the yarn itself, preventing sliding on the side surface and thus allowing its regular winding on the support.        simple notch, possibly equipped with a yarn-blocking slit: consists of an opening, which engages the entire thickness of the tubular support body and has a profile in which at least one oblique portion is formed, specifically slightly inclined with respect to the direction perpendicular to the longitudinal axis of the tubular body and having the function of easing the interception and attaching of the end of the yarn on the body itself. A slit can be associated with the oblique portion which engages the yarn and blocks it preventing it from sliding on the side surface and therefore allowing its regular winding on the support.        window notch, possibly equipped with a yarn-blocking cut: consists of a simple notch formed completely inside the side surface of the tube and thus equipped with a closed perimeter with which is, possibly, associated a circumferential cut which has the task of blocking the yarn, to allow its regular winding on the support.        
At the current state of the art the yarn-gathering indentation, associated or not with a yarn-blocking indentation, is formed on the side surface of the tubular body and more precisely on one of the two edges, or close to one of them, which defines one of the two ends of the side surface of the body itself.
Nevertheless this constructive solution allows the possibility of attaching a single yarn to the tubular body and therefore it is possible to realise the winding of a single hank of wound yarn for every single tube.
Moreover, with said constructive solution of the known type the tube, as well as, obviously, being able to be mounted on winding machines on a single side, is suitable for being mounted only on a winding reel which has a specific direction of rotation, that corresponding to the inclination of the yarn-capturing indentation formed on the tube itself for which reason if winding machines are used with winding reels which rotate with opposite directions of rotation it is necessary to have scored two different types of “tubes”, to the great disadvantage of the productivity.